Switchable' Solvents Could Lead To More Environmentally Friendly Chemical Manufacturing

Aug 01, 2005

Researchers from Queen's University and the Georgia Institute of Technology announced on Aug. 24 they have discovered a new environmentally friendly way to make certain chemicals for pharmaceutical and other industries, such as plastics, pesticides, dyes and fragrances.

The team has developed new solvents (liquids that dissolve other substances) that are both cleaner and cheaper when used in the production of many chemicals. Because each step in a chemical process often requires a different solvent, there can be a great deal of waste which is both costly and damaging to the environment.

"We all want the products of the plastics and pharmaceutical industries, but we don't want the pollution," said Queen's chemist Dr. Philip Jessop, Canada Research Chair in Green Chemistry. "Our research is seeking ways to decrease the amount of solvent waste generated by these companies." In the ratio of waste-to-product, pharmaceutical and other "fine chemical" industries are far dirtier than the oil industry, he noted.

These new "switchable" solvents discovered by Jessop's team change their properties when alternately exposed to carbon dioxide and nitrogen, making it possible to re-use the same solvent for multiple steps in a chemical process, rather than discarding and replacing the solvent after each stage.

The team includes Queen's Chemistry Department graduate students David Heldebrandt and Xiaowang Li, and Georgia Institute of Technology's Drs. Charles Eckert and Charles Liotta, both winners of 2004 Presidential Green Chemistry Challenge Awards.

The organic solvents tested by this research group are known as ionic liquids: a salt that is molten at room temperature, or near-room temperature. "They have been widely hailed as environmentally benign because they have no vapor pressure, and they also have some unusual properties," said Eckert, a professor in the School of Chemical and Biomolecular Engineering at Georgia Tech.

However, the new ionic liquids are different because exposure to nitrogen gas causes them to change back into regular (non-ionic) liquids. "It's a potential tool for benign and economical processing in the manufacture of high-value-added specialty chemicals, such as pharmaceuticals," Eckert said.

Green chemistry refers to the development of chemical products and processes that reduce or eliminate the use and generation of hazardous substances. Rather than focusing on the natural environment and pollutant chemicals in nature, this type of chemistry seeks to reduce and prevent pollution at its source. "We're concerned with pollution prevention rather than treatment," said Jessop. "That's a much more economical way to approach the problem."